Last Sunday, the 37-year-old completed an epic race in which his only competitor was the clock, and this effort made those earlier 100-milers pale in comparison.

Koerner and Mike Wolfe, a lawyer from Missoula, Mont., ran the 223-mile John Muir Trail in the Sierra Nevada mountains in 3 days, 12 hours and 41 minutes, the fastest known time — FKT — for completing that course. Their time shaved 1 hour and 32 minutes off the FKT set in 2009 by Brett Maune, a 30-year-old laser physicist from Los Angeles.

Both Koerner and Wolfe are sponsored by outdoor gear retailer The North Face.

Though Koerner has completed most of his 100-mile races in far less than 24 hours, he's no stranger to the multiday sufferfest. In 2003, he set a new FKT on the 500-mile Colorado Trail in 91/2 days. That effort, he believes, gave him valuable insights for last week's outing.

"I knew the little things you need to do to take care of yourself. You have to constantly be eating and drinking. Foot care is of the utmost importance, keeping dry socks and shoes and putting on a lubricant to avoid blisters and chafing," says Koerner.

Running, he says, may not describe much of the pair's adventure on the steep John Muir Trail. Their FKT a route in California began at the Mount Whitney portal and ended at Happy Isles in Yosemite National Park. That route tops six mountain passes above 11,000 feet and rarely dips below the 8,000-foot mark.

"Much of the uphill sections were just a purposeful hike, and that was the plan," Koerner explains. "But what we found was that even a lot of the downhills were very unrunnable because it was just so rocky and had a lot of switchbacks."

The physical toll exacted by this difficult terrain has stymied many attempts at a new FKT, including one last summer by Ashland ultrarunners Jenn Shelton and Ryan Ghelfi.

In addition to the terrain, the pair faced frost at night and sunburn during the day, at least when they could see the sun.

"Around the 150-mile mark near Vermillion Lake, we passed through this heavy forest fire smoke that was so thick you couldn't even see for a mile, and this course is probably the most beautiful stretch of trail in the U.S.," says Koerner.

Perhaps what most distinguishes the multiday effort from the single-day, merely pedestrian 100-miler is sleep. Or rather, the lack thereof.

"We'd get to sleep for two hours, and it was like the sweetest two-hour sleep ever," Koerner recalls of the respite they permitted themselves on each of the two nights, as well as a one-hour nap.

Fatigue accumulated with sleep deprivation, mental as well as physical. Late in their run, shortly before they were scheduled to pull into a campground where their crew awaited, Koerner's mind indulged in wishful thinking.

"The rocks started to look like a lot of tents, and they looked really comfy to go get into," Koerner laughs. Another hallucination he experienced was seeing trees turn into people.

The mental challenge was perhaps more daunting than the physical one. After running so many ultramarathons, says Koerner, "I've perfected the art of suffering."

The two North Face runners had a crew to cook meals at night, carry sleeping bags and provide companionship for a few miles at a time on the trail. Although those hot meals included selections of the traditional dehydrated backpacker fare, as well as grilled cheese and hamburgers, the daily trail food was far different.

For future reference, says Koerner, salami and cheese, tortillas and Nutella with bagels don't digest easily, and they slow the pace while the stomach catches up. Instead, he stuck mostly with the sugary Gu sports gel.

Early on in their adventure, the pair tried not to focus on the clock, even though there were long stretches when their forward progress amounted to a mere 3 miles per hour. Even so, before the first day was through, simple math proved there was no way they'd go under the three-day mark, their dream goal. Time was lost on small, unanticipated breaks.

"There's a lot of stopping for things like filtering water on the trail. We made a lot of rookie mistakes," Koerner admits.

It was food, rather than pace, that caused the biggest scare, according to Jennifer Benna, who along with her husband, JB, served as the primary crew for this run.

"We got this text from Hal: 'We're in trouble! We have only a half bag of Oreos, 2 Gu-s, and a half bag of beef jerky,' " recalls Jennifer. "Another runner was going to resupply them, and they missed him by 20 minutes."

JB Benna then stuffed a pack full of food and headed up a connector trail. He ran 15 miles before encountering the starving runners.

"They were just kind of staggering along," JB says. "They ate almost everything right there, but we still had 19 miles to go (to get to the sleeping bags and hot food)."

By the time Koerner and Wolfe had crossed into Yosemite National Park, and were down to 25 miles and 8 hours just to equal the existing record, they realized the FKT was slipping away, assuming they'd finish at their current pace.

"The last 25 miles are really runnable, a lot of downhill. If anything was going to happen, it was going to happen there," Koerner explains.

With 10 miles to go, they faced a make-or-break decision. Going for broke, they ran more than 7 miles in one hour, double their speed at the time. Koerner then looked at his watch and realized they were going to break the record.

His body, however, had other plans.

They reached the valley floor in Yosemite National Park, thinking they were at the end of the trail. A crew member yelled that four miles remained, but Koerner's last drop of adrenaline was spent, and the pain, fatigue and mental exhaustion consumed him. He couldn't run.

"I kind of shuffle-walked, and it took a lot of reassurance from our crew to keep going," Koerner recalls. "It was only the last 300 yards that it felt like a prideful walk."

Through the many low points over those 31/2 days, it was the FKT goal that initially kept Koerner from throwing in the towel, as was the prospect of seeing friends at each scheduled rendezvous. Early on, though, his will was tested. The runners stopped briefly to rest and considered taking a nap in 30-degree weather, alone in the dark stillness of an unfamiliar forest.

"I started to get cold, so we had to keep going," says Koerner. "It was a matter of survival."

For more on the history of the John Muir Trail FKT, see http://fastestknowntime.proboards.com/thread/21

Daniel Newberry is a freelance writer living in the Applegate Valley. Email him at dnewberry@jeffnet.org.